a) Field of the Invention
This application was published under PCT Article 21(2) in the German language with an English abstract: this is a request for a CPA application under 37 C.F.R. 1.53(d) (continued prosecution application) of pending prior application 09/582,814 filed Nov. 4, 1999 as PCT/EP99/08445 claiming foreign priority to DE 198 51 000.4 filed Nov. 5, 1998 to which priority is hereby claimed. The invention is directed to an arrangement with a projector and a deflecting mirror in which the image projection proceeding from a projection direction impinges on the deflecting mirror which is mounted so as to be movable in two spatial directions and whose mirror surface deflects the projection beams at an elevation angle and an azimuth angle. A projection arrangement of this type can also be called a drawing projector, since a static or moving image is generated, projected onto a projection surface, and moved on the latter.
b) Description of the Related Art
For front projection, the projection surface is a wall (e.g., projection screen) or, in the case of rear projection, a screen (e.g., ground glass screen). The projector is not limited to a certain type of image generation. Projectors which write the image by means of a brightness-modulated and/or color-modulated light beam can be used. These projectors are also known as laser projectors. However, image-forming projectors which generate an image proceeding from an object plane internal to the device as is known, for example, in CRT, LCD, DMD or slide projectors can also be used.
A deflecting device for an image generated by a laser beam is known from U.S. Pat. No. 5,365,288 DEWALD. The image is rotatable by itself by means of a K-mirror arrangement and is then deflected in such a way by a mirror mounted on two axes that the generated image can be deflected in a defined spatial area. The arrangement of the elements for the image deflection is carried out in such a way that the image is generated in a device standing on the floor and is directed to the deflecting mirror proceeding from this floor position.
In relation to a horizontal plane through the axis of rotation of the deflecting mirror, the practical useful deflection angle area resulting from this arrangement
is limited toward the floor due to the required device dimensions and can be, at most, approximately 45xc2x0 without substantial image shadowing, and
can be at most 30xc2x0 in practice toward the zenith due to the mirror dimensions increasing toward infinity.
Therefore, the observer is only afforded limited viewing possibilities which are more sharply limited in the direction of the zenith than in the direction of the floor. However, this conflicts with the customary mode of observing images that are generally projected xe2x80x9cskywardxe2x80x9d, another reason for this being to prevent shadowing caused by other observers or by structural parts. It is impossible to generate images in the vicinity of the zenith with this arrangement.
It is the primary object of the invention to increase the area of possible image presentation on a given projection surface in an arrangement of the type mentioned above. The area in which a comparatively small image can be presented within a projection surface which is large in proportion to the image size, especially in a projection dome, is to be expanded. The position of the display area should correspond to the normal viewing habits of the observer and it should also be possible to display an image in the vicinity of the zenith and in the zenith. In this respect, a high-quality monochromatic, black-and-white, or color image can be displayed at relatively little expense and, at the same time, can be moved on the projection surface, in particular, fast enough so that the observer can substantially follow the movement of the image. Further, an arrangement of a plurality of projectors is possible, wherein mutual shadowing is also minimized in this case and the area in which it is possible to display images is maximized for all projectors.
According to the invention, a projection arrangement with a projector and a deflecting mirror are suggested, wherein the image projection, proceeding from a projection direction along a principal projection axis, impinges on the deflecting mirror which is supported so as to be movable in two spatial direction and whose mirror surface deflects a projected light bundle at an elevation angle and at an azimuth angle onto a projection surface standing on the ground, wherein the image projection is effected from the direction of a zenith at an angle xcex2 which is less than 60xc2x0 in relation to a vertical line from the zenith, and the deflecting mirror is arranged on the ground, wherein, further, the projected light bundle can be deflected toward the projection surface and an image can therefore be generated on the projection surface and moved on the latter.
By xe2x80x9czenithxe2x80x9d is meant the zenith of the dome of the sky or the zenith of an artificial dome, e.g., in a planetarium. When it is stated that the deflecting mirror is arranged on the ground, this does not mean that it must lie directly on the ground. It can be arranged far above the surface of the ground by means of a holder or can be fastened to a wall above the surface of the ground or can also be suspended from a ceiling. However, it is essential that the projection is carried out proceeding from the direction of the zenith onto the mirror surface of the deflecting mirror. The indicated quantity of angle xcex2 signifies that the direction of the light bundle impinging on the deflecting mirror comes from the direction of the zenith. By means of the arrangement according to the invention, a surface region that is substantially larger compared to the prior art is achieved, for example, in a projection dome of a planetarium, when an image is displayed, and the image display on the projection surface is not disturbed by shadowing.
Further, the shadowing caused by projectors, other installed items or observers can be minimized. In particular, the display of the image reaches the surface region around the zenith without restrictions and without shadowing.
In an advantageous development of the invention, an image is generated by the projected light bundle only in a partial region of the projection surface and is then movable within the entire area of this projection surface. The movement can be carried out comparatively quickly because the relatively massive projector is stationary and only the comparatively small mass of the deflecting mirror must be moved.
The image should not fill up the entire projection surface statically as is the case, for example, in a cinema, but, rather, should be movable within the display area on the projection surface. The image can be equal to or greater than the projection surface for some applications. In this case, portions of the image cannot be displayed during the movement of the image. For many applications, however, it is sufficient when the size of the moving image is less than 90% in relation to the size of the projection surface. This is advantageous, for example, for image tracking for displaying set designs in entertainment applications when images are to be projected on backdrop arrangements. In this case, the image contents can always be displayed in their entirety. In many applications, the image is a comparatively small image, for example, of a planet or aircraft, that is moved on the projection surface, e.g., over the dome of the sky. However, the size of the image to be displayed by the projector can also be less than 1% of the projection surface.
The image size can be continually adjusted through the realization of a zoom function, so that, for example, an approaching or receding vehicle can be simulated in a realistic manner. This zoom function can be realized by means of known zoom optics or in an image-generating computer.
The control of the deflecting mirror can advantageously be carried out relatively simply when the axis of rotation for adjusting the elevation angle extends vertical to the principal projection axis and the axis of rotation for adjusting the azimuth angle coincides with the principal projection axis. In this case, no image distortions occur as a result of the deflection of the image by the deflecting mirror. It is particularly advantageous when the direction of the principal projection axis to the deflecting mirror is a line parallel to the vertical line from the zenith. In this case, angle xcex2 is 0xc2x0. One of the axes of rotation of the deflecting mirror then contributes only one movement component to the azimuth position and to the elevation position of the image. This enables a particularly simple correlation of the image position in the area of the projection surface.
When the direction of the principal projection axis onto the deflecting mirror lies in the vertical line from the zenith of a spherical projection dome, a movement of the image by 360xc2x0 can be realized particularly favorably. A particularly advantageous arrangement is achieved when the projector is arranged in the zenith of a projection dome and the deflecting mirror is arranged on the floor of projection dome, wherein the axis of rotation for the adjustment of the azimuth angle coincides with the vertical line from the zenith. The projector is then located outside of the projection dome and the coupling in of radiation is carried out through a small opening in the zenith of the projection dome. In this case, only the deflecting mirror is still arranged inside the projection dome. Another advantageous arrangement is achieved when the deflecting mirror is arranged in the center of a spherical projection dome. The projection distance from all areas of the projection dome is identical in this case. The size of the image is then identical at all angle positions without further steps.
In particular, this arrangement facilitates image generation by means of image-forming projectors, for example, slide projectors, LCD projectors or DLP projectors, since the possible area of the depth of focus of projectors of these types is only relatively small and no additional steps are required in this case for adjusting or producing the image focus. When projection is carried out with projectors of these types from outside the spherical center or the image is directed onto an aspherical projection wall, a readjustment of the image focus as a function of the image position is compulsory. With larger images, partial areas of the image can also be out of focus.
This problem does not occur when using a projector which works with a writing, essentially parallel, laser light bundle. Images generated in this manner are focused within a very large area amounting to several meters at any projection distance. Such projectors are known as xe2x80x9claser projectorsxe2x80x9d.
It has been shown in practice that the image size is perceived by the observer as stationary when the deflecting mirror is arranged in relation to the projection surface in such a way that the projection distance from every point of the projection surface deviates from an average projection distance by less than +/xe2x88x9210%. This result is achieved especially when the observer lacks a comparison scale. A zoom function of the projector for readjusting the image size is not absolutely necessary. However, for subordinate applications, a deviation of +/xe2x88x9220% is also acceptable.
The size of the area in which a good-quality image is movable on the projection surface without shadowing by a deflecting mirror that is not too large depends first on the overall size of the projector or its subassemblies located in the projection dome. As will be shown subsequently in the embodiment examples of the invention, this factor can be minimized absolutely. The size of the projection surface that can be utilized for image projection is further determined by the position of the axes of rotation of the deflecting mirror relative to the projection surface. The height of the deflecting mirror in relation to the horizon given, for example, in a projection dome, is a critical determinant for the size of the accessible area for displaying the image. When the axis of rotation generating the elevation angle lies above the horizon, the display area is reduced; when it lies below the horizon, the area in which it is possible to display the image is increased. In extreme cases, the projection dome is a sphere, the projector is located at the zenith and the deflecting mirror is located opposite the zenith on the ground. There are virtually no restrictions with respect to the shape of the projection surface, especially with a laser projector, because of the virtually unlimited depth of focus. The projection surface can be the inner surface or the outer surface of a sphere, a part of a sphere, or a layer of a sphere, or an aspherically curved surface corresponding to the basic shapes mentioned above. However, it can also be a plane surface or can be formed of a plurality of parts of such a surface, or can be shaped in a completely irregular manner and/or be moved dynamically.
A particularly favorable use of space and a very practical construction are achieved when a stationary path-folding or reflection mirror which deflects the light bundle proceeding from the projector is arranged relative to the projector. The choice of how and where the projector is arranged in relation to the projection surface is relatively open. It is only necessary to meet the condition that the light bundle travels from the direction of the zenith after deflection through the reflection mirror.
In an image-forming projector, the reflection mirror is arranged behind the projection objective in the direction of radiation. With a laser projector with a writing light bundle, the reflection mirror is provided behind the deflecting device for scanning lines in the image or behind the angle-transforming transformation optics that are used in most cases. The reflection mirror is advisably fixedly connected with the projector. Owing to the simplicity of control with angular coordinates, it is further advisable when the stationary reflection mirror is at an angle of 45xc2x0 to the principal projection axis from the projector. In this regard, it is particularly advantageous when the projector itself is at an angle of 90xc2x0 to the azimuthal axis of rotation of the deflecting mirror. However, the reflection mirror can also be movable in order to generate special image effects. For example, the light bundle which is directed to the deflecting mirror can be redirected to another deflecting mirror with a different mirror position by means of a controllable reflection mirror. In this way, sudden image movements can be generated, for example, when changing between the two deflecting mirrors which are arranged next to one another and have different mirror positions.
A laser projector comprises at least one brightness-modulated and/or color-modulated laser radiation source and a deflecting device for scanning the light bundle in two dimensions. For the use of laser projectors in projection rooms, it is particularly advantageous when the brightness-modulated and/or color-modulated laser radiation source and the projection head are optically connected with one another in a projector of this type by a light-conducting fiber. The laser radiation source is a monochrome laser radiation source or a red-green-blue laser radiation source by which light can be efficiently coupled into a light-conducting fiber. The spatial separation of the light source and projection head which is made possible by the light-conducting fiber connection provides many design possibilities with respect to how the installation of the projector can be carried out, for example, in a projection dome.
The spatial separation of the subassemblies or component groups does not cause any problems with respect to the setup of a contemporary, relatively heavy and large laser beam source adjacent to or under the projection dome or with respect to the arrangement of the comparatively small projection head in the projection dome or on the projection dome. Even arranging the projection head in the zenith of a projection dome does not cause problems in this case. As subassemblies become smaller and lighter with progressing development, it will become easier to mount the projection system in a housing.
The projection head contains a horizontal-line mirror and a vertical-line mirror for scanning the light beam. Further, transformation optics which increase the scanning angle are arranged downstream in the direction of light when required by the projection ratios (the image size to be achieved at a given projection distance). These transformation optics can also contain a controllable zoom function when the image size is to be adjusted or varied during the image display. The electronic control of the zoom factor is carried out as a function of the desired image size on the projection surface, wherein changes in the image size due to changes in the projection distance can also be compensated for.
But the invention can also be realized using image-forming projectors, for example, with a film projector, a slide projector, an LCD projector or a CRT projector. In projectors of the types mentioned above, a projection objective is generally used in order to be able to adjust the desired image size. In this case, temperature radiators are conventionally used as light sources. The projector can also be divided up into the subassemblies of light source and projection head in this case. In contrast to the laser projector, the projection head contains the object plane with a projection objective associated with the latter.
The optical connection between the subassemblies can also be produced via a light-conducting fiber or bundled light-conducting fibers. The advantage that the heat output occurring during operation of a temperature radiator need not be given off in the projection space is applied in particular in this case.
However, a laser radiation source can also be used in image-forming projectors, although it must be expanded for illuminating the object field. In this case, the light transmission from the laser light source to the object field is likewise provided via a light-conducting fiber. With a stationary installation, the possibility of light transmission between the light source and projection head in free space, irrespective of the type of projector, is also a particularly advantageous variant; in this case, when the light source is set up outside of the projection space, the light must be guided through an opening in the projection screen or in the projection dome.
The projection systems described above can be combined with a pilot laser for training purposes and measurement purposes. In this connection, the wavelength of the pilot laser beam is not the same as the wavelengths of the projection beams. The pilot laser beam can be coupled into the beam path in such a way that it represents a fixed point in the deflected image and is movable together with the image. The reflection mirror is particularly suitable for coupling in the pilot laser beam; this reflection mirror is transparent for light of the wavelength of the pilot laser beam and reflects all other wavelengths. However, the pilot laser beam can also be coupled into the beam path of the projection arrangement at another location, for example, via an additional coupling-in mirror, wherein coupling in should be carried out subsequent to the deflecting system and transformation optics because of the wavelengths of the pilot laser beam which lie outside of the range of visible light. The direction of the pilot laser beam can also correspond to the position of the principal projection axis in particular or can be correlated to a determined object in the projected image.
The movement of the image can be tracked by a direction-sensitive receiver that is adjusted to the wavelength of the pilot laser beam, or an automatic or manual image tracking can be detected and evaluated.
The above description of the projection arrangement working with a projector and a deflecting mirror also shows advantages when more than one projector is set up in a projection space. For example, a first projector can project a scene filling up the projection surface and a second projector, by means of the deflecting mirror, supplies a comparatively small image which is movable within the scene and which can be displayed completely independent from this scene.
In another variant, a plurality of projectors are directed to a projection surface with respective associated deflecting mirrors. Accordingly, for example, three images showing different objects can be moved over the projection surface independently from one another. Each of the images can show an aircraft, for example. In so doing, the deflecting mirrors can be arranged next to one another in horizontal direction, wherein the directions of the light bundles impinging on the mirror surfaces of the deflecting mirrors also proceed from the direction of the zenith in this case.
The deflecting mirrors can also be arranged one above the other in vertical direction. In addition, the deflecting mirrors can lie next to one another. However, it is advisable when projectors with reflection mirrors are used and the directions of the principal projection axes of the light bundles coincide following the beam deflection through the respective associated reflection mirrors.
All deflecting mirrors are accordingly arranged at a short distance exactly one above the other. In this way, the projection ratios are virtually identical for all projectors, since the projection of all images is effected proceeding from virtually the same location. In this case, the condition that the projection distances of the projectors from the average projection distance is less than +/xe2x88x9210% can easily be satisfied.
The enlarged angular range in which images can be displayed without any shadowing is particularly advantageous compared with known projection arrangements. This advantage comes into play particularly when more than one projector must be arranged in a projection space. Moreover, the position of the angular area, for example, in relation to a position of the projector in a projection dome, is more favorable because now images can be displayed in the area of the zenith until far below the horizon. When using a projector working with a writing laser light bundle, the advantages that images produced in this way have a virtually unlimited depth of focus and that a very extensive correction of image errors can be carried out are particularly useful.
In the following, the invention will be described more fully by way of example with reference to the drawings.